1. Field of the Invention
The present invention relates to an ink-jet thermosetting ink composition used for forming a cured layer of a predetermined pattern, such as a coloring layer (ex., a pixel part) on a substrate of a color filter, a production method for the ink-jet thermosetting ink composition, and a method for producing a color filter using the ink-jet thermosetting ink composition.
2. Description of the Related Art
Recently, with development of personal computers, in particular, development of portable personal computers, demand for a liquid crystal display, particularly for a color liquid crystal display device has been increased. However, since the color liquid crystal display device is expensive, cost reduction is more and more required, in particular, cost reduction for a color filter, whose proportion in the cost is high, is highly requested.
In general, as shown in FIG. 1, a color liquid crystal device (101) has a structure including a color filter 1 and an electrode substrate 2 such as a TFT substrate facing with each other with a gap part 3 of about 1 to 10 μm therebetween filled with a liquid crystal compound L and the circumference thereof sealed by a sealing material 4. The color filter 1 has a structure with a black matrix layer 6 formed in a predetermined pattern for blocking the light an the boundary part between the pixels, a pixel part 7 with a plurality of colors (in general, the three primary colors of the light including red (R), green (G) and blue (B)) for forming the pixels arranged by a predetermined order, a protect layer 8, and a transparent electrode layer 9 laminated in this order on a transparent substrate 5 from the side closer to the transparent substrate. Moreover, an orientation layer 10 is provided on each inner surface side of the color filter 1 and the electrode, substrate 2 facing therewith. Furthermore, pearls 11 with a certain particle size are dispersed in the gap part 3 as the spacer for maintaining the cell gap between the color filter 1 and the electrode substrate 2 constantly and evenly. By controlling the light transmissivity of the liquid crystal layer on the rear side of the pixels colored in each color or on the rear side of the color filter, the liquid crystal layer can be operated as a shutter so as to obtain a color image.
In the case fine particle-like pearls 11 as shown in FIG. 1 are dispersed as the spacer, the pearls are dispersed randomly regardless of whether they are provided on the rear side of the black matrix layer 6 or on the rear side of the pixels. In the case the pearls are disposed in the display area, that is, in the pixel part, the backlighting light transmits in the pearl part, and furthermore, the display image quality is deteriorated significantly due to the disturbance of the liquid crystal orientation in the vicinity of the pearls. Then, as shown in FIG. 2, instead of dispersing the pearls, pillar-like spacers 12 having a height corresponding to the cell gap can be formed in an area on the inner surface side of the color filter, the area being superimposed with the position at which the black matrix layer 6 is formed.
In FIG. 2, a color liquid device 102 is provided.
Detail portions of the color filter such as the pixel part, the pillar-like spacers, the protect layer or the like can be provided by forming a coating layer of a predetermined pattern using a resin, drying and solidifying the coating layer, and further as needed curing by the cross-linking reaction.
To the resin layer comprising the details, not only a performance to a certain degree is required in terms of the common physical properties as a layer such as the adhesion property, the evenness of the layer thickness, the strength, the hardness and the heat resistance which does not cause thermal shrinkage or decrease of the layer thickness in the color filter production process, but also a particularly high performance is required in terms of the characteristics regarded important specifically for each detail part. For example, to the resin layer as the pixel part whose optical characteristics regarded important, it is required to have the excellent characteristics particularly in terms of the pattern shape accuracy, the evenness of the layer thickness, the transparency, the coloring property and the discoloration resistance. To the resin layer as the black matrix layer, it is required to have the excellent characteristics particularly in terms of the pattern shape accuracy and the light shielding property. To the resin layer as the pillar-like spacer for maintaining the cell gap, it is required to have particularly the excellent strength and the excellent size stability even in the case of forming in a relatively large thickness. Moreover, to the resin layer as the protect layer 8 covering the pixel part, sufficient hardness and sufficient adhesion property are required for protecting the pixel part, the excellent transparency and the layer thickness evenness are required so as to avoid an adverse effect to the color of the pixels, and furthermore, the non-pollution properties, such as the passivation property capable of inhibiting transfer of the polluting substance from the coloring layer side to the liquid crystal and the non-elution property without the risk of eluting the protect layer itself to the liquid crystal, are required so as not to pollute the liquid crystal compound sealed in the gap part 3. Furthermore, to the protect layer 8, a sufficient solvent resistance so as not to be dissolved or swelled at the time of coating an orientation layer forming coating liquid thereon, and sufficient hot (or warm) pure water resistance and solvent resistance are required so as not to generate thickness reduction or fall-off at the time of washing with hot pure water or an IPA (isopropanol).
Conventionally, as a method for forming a protect layer for a color filter, a method of coating, on a surface to be coated, a coating liquid containing a photo-setting type resin such as an UV curing type and an ionizing radiation type, drying and carrying out selective exposure and development by a photolithography process, or a method of coating, on a surface to be coated, a coating liquid containing a thermosetting type resin by printing or the like in a predetermined pattern, drying and heating the obtained coating layer so as to form a cured resin layer with a predetermined pattern as the details of the color filter, are well known.
Moreover, as a method for forming the pixel part of the color filter, for example, a dying method can be presented. In the case of using the dying method, first a layer of a water-soluble polymer material as a dying material is formed on a glass substrate, patterning the same in a desired shape by a photolithography process, and soaking the obtained pattern in a dying bath so as to obtain a colored pattern. By repeating the operation for three times, R, G and B color filter layers can be formed.
Moreover, as another method, a pigment dispersing method can be presented. According to the method, first a photosensitive resin layer with a pigment dispersed therein is formed on a substrate and it is subjected to patterning by a photolithography process, and a single color pattern is obtained. Furthermore, by repeating the same operation for three times, R, G and B color filter layers can be formed.
As still another method, an electro-deposition method, a method of dispersing a pigment in a thermosetting type resin, printing three times for R, G and B, and thermally setting the resin, or the like can be presented.
In the case of using the photo-setting type resin, a cured resin layer of a desired pattern can be formed on a desired position of a surface to be coated by exposing the coating layer in a desired pattern, however, there is a risk of pollution leading to the display failure by transfer of the low molecular weight components existing essentially in the coating liquid such as a monomer, a photo polymerization initiator or the like into the liquid crystal.
In contrast, in the case of using the thermosetting type resin, although the risk of pollution by the transfer of the low molecular weight components to the liquid crystal is low compared with the case of the UV curing type resin, it is difficult to form in a complicated pattern compared with the case of the photo-setting type resin.
Moreover, in the case of forming the pixel part, the same process should be repeated for three times in either method for forming the pixels for the R, G and B three colors, and thus a problem of cost increase and a problem of decline of the yield due to the repetition of the same process, are involved.
As a production method for a color filter capable of solving the problems, a method of forming a coloring layer (pixel part) by shooting an ink onto the substrate surface by the ink-jet method has been proposed (the official gazette of the Japanese Patent Application Laid-Open No. S59-75205).
In order to form the pixels by shooting the ink according to an accurate pattern by the ink-jet method, sustainability and straightness are required at the time of the ejecting operation from the recording head. However, in the case where the evaporation rate of the ink is too high, the ink viscosity is increased drastically at the nozzle end of the recording head so as to exhibit multiple elections of the ink droplets (“deflection of shooting direction” in other word), or choking is generated in the case of intermittent ejection with a time interval so as to disable the re-ejection,
Furthermore, as shown in FIG. 3, in the case where the ink is wetly spread on the peripheral surface 13a of an orifice of the head 13, the ink droplet 14 ejected in the front direction Vx is pulled in the ink spreading direction Vy so as to exhibit multiple ejections. Therefore, due to the wetly spreading of the ink on the peripheral surface of the orifice, straightness of drop direction is further deteriorated.
Moreover, in the case where the drying rate is too high at the time of shooting a colored ink onto the substrate by the ink-jet method, the ink layer surface is solidified in the waved state or the inclined state immediately after the ejection so that the leveling is insufficient. In contrast, in the case where the drying rate is too low, it can hardly be dried completely by a heating process or even in the case where it can be dried, the efficiency is poor. Therefore, in consideration of only the ejection performance, an ink hardly dried can be used, however, in order to completely dry the ink layer, an appropriate drying property is needed as well.
As a coloring agent contained in the pixels or the black matrix of the color filter, pigments are used frequently. However, in the case where the pigment dispersing property of the color filter ink is poor, choking is generated at the nozzle part of the recording head due to aggregation of the pigment particles with each other. Therefore, in the case of using the pigment as the coloring agent, the pigment dispersing property casts the influence on the ink ejection performance.
According to the official gazette of the Japanese Patent Application Laid-Open No. H11-202144, an ink for a filter containing 60% by weight or more of a solvent with a 150° C. to 250° C. boiling point and at least one selected from the group consisting of a glycerol, a diethylene glycol and an ethylene glycol as the wetting agent, is disclosed. Since the wetting agent is provided in the ink disclosed in the official gazette, the ink can hardly be dried at the nozzle end of the recording head so that choking can hardly be generated.
Moreover, according to the official gazette of the Japanese Patent Application Laid-Open No. 2000-310706, an ink-jet method type resin composition for the color filter, which contains a coloring agent, a binder resin and a solvent with a 250° C. or higher boiling point at an ordinary pressure, is disclosed. Since a high boiling point solvent is used in the ink-jet method type resin composition for the color filter disclosed in the official gazette, the ink can hardly be dried at the nozzle end of the recording head so that choking can hardly be generated.
However, after ejection of the inks disclosed in the above official gazettes onto the substrate, the wetting agent and the high boiling point solvent, which can hardly be dried, remains to the final process in the process of drying the ink layer so that they can hardly be dried completely.
Moreover, in the case of forming the details of the color filter with a thermosetting type resin, it is common to utilize polymerization and/or the cross-linking reaction of the acid component and the epoxy component. In order to improve the strength, the hardness, the passivation property or the like of the cured resin layer, it is preferable to make the cross-linking density of the cured resin layer larger. In order to increase the cross-linking density of the epoxy-based thermosetting type resin layer, it is preferable to increase the reaction point concentrations (or reaction site concentrations) of the acid component and the epoxy component in the coating liquid or the coating layer formed with the coating liquid as much as possible and/or make the reaction equivalences of the acid component and the epoxy component as close as possible. However, since the acid component can hardly be dissolved in an organic solvent, it has been difficult to have a large amount of acid component coexisting in the coating liquid (in the reaction system). Moreover, even in the case where a sufficiently large mount of the acid component corresponding to the epoxy component amount can coexist in the coating liquid, a deterioration in the time passage stability is caused due to too high the reactivity of the coating liquid, as a result, the viscosity change (in particular the viscosity rise) can easily be generated in a short time so that there is a risk of difficulty in stable ejection by the ink-jet method.
According to the official gazette of the Japanese Patent Application Laid-Open No. H04-218561, a one liquid type thermosetting composition containing a carboxylic acid blocked product which is produced by blocking a carboxylic group of a polycarboxylic acid by a vinyl type double bond containing compound and a compound which has two or more reactive functional groups to be chemically bonded with a carboxylic acid reproduced from the carboxylic acid blocked product is disclosed. Since this thermosetting type composition makes the polycarboxylic acid, in a state that it is in a form of the blocked product which is not reactive with the reactive functional groups such as an epoxy group, coexist in the thermosetting reaction system, a good storage stability can be provided so that it can be utilized for a paint, an ink, and adhesive, a molded product or the like. However, in the official gazette of the Japanese Patent Application Laid-Open No. H04-218561, application of the thermosetting type composition to a color filter is not discussed.